1. Field of Invention
The present invention relates to 4-nitroso anilines of the formula I ##STR1## wherein R.sub.1 and R.sub.2 are the same or different, and are H, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 hydroxyalkyl or polyhydroxyalkyl, C.sub.1 -C.sub.6 alkoxyalkyl or polyalkoxyalkyl, C.sub.1 -C.sub.6 amino alkyl, C.sub.1 -C.sub.6 dialkylaminoalkyl, or R.sub.1 and R.sub.2 taken together with the nitrogen atom to which they are attached may be a heterocyclic ring selected from the group consisting of morpholino, pyrrolidino, piperidino and piperazino; R.sub.3, R.sub.4, R.sub.5, and R.sub.6 can be the same or different, and are H, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 hydroxyalkyl or polyhydroxyalkyl, hydroxy, C.sub.1 -C.sub.6 alkoxy, C.sub.1 -C.sub.6 hydroxyalkoxy or polyhydroxyalkoxy, or halogen; and cosmetically acceptable salts thereof. The instant invention also relates to the use of the compounds of formula I as direct dyes and to compositions for dyeing keratin fibers containing compounds of formula I.
2. Description of the Prior Art
4-nitroso anilines are known in the art. U.S. Pat. Nos. 4084052 and 4023926 disclose examples of such compounds as reactants in processes for producing other compounds of interest. In the reactions disclosed the nitroso group is lost.
U.S. Pat. No. 3970423 discloses solutions of 4-nitroso-N, N-disubstituted anilines in isopropanol. The disclosed 4-nitroso-N,N-disubstituted anilines function as intermediates which undergo further reaction to produce substituted p-phenylenediamines.
The Colour Index discloses several nitrosophenols as mordant dyes which form color upon complexation with a metal. The compounds disclosed are not anilines and merely serve as intermediates to dyes.
British patent 2141437 discloses nitroso compounds for synthesis of indoaniline and indophenol compounds.
Color Chemistry--Synthesis, Properties and Applications of Organic Dyes and Pigments--Zollinger VCH, 1987, Chapter 6--Nitro and Nitroso Dyes, pp 83-84, discloses hydroxy nitroso compounds which are used exclusively as metal complex dyes.
Although there is a considerable amount of prior art relative to the 4-nitroso anilines, we are unaware of any prior art appreciation of the use of such compounds as direct hair dyes.